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The Lost OP Wiki: Revo - Setting Home Location
= Revo - Setting Home Location = Setting the Home Location is an essential part of properly configuring the Revolution flight controller. The Home Location is used during sensor calibration in order to determine the local magnetic fields at the point where the device is calibrated. Home Location is also required when making use of the autonomous flight features. All GPS receives use a mathematical model known as the World Geodetic System (WGS84) reference to represent their position with respect to the earth's surface, and the altitude referenced to the mean sea level. In order to more accurately determine the altitude of the vehicle, the OpenPilot system needs to take into account the geoid separation at the current location. There are two methods of entering the Home Location. The first is a manual process of using the map in the GCS and entering the value yourself. This method does not require a current GPS fix. The second method involves letting the Revolution set this value itself automatically from data obtained from the GPS receiver. Each of these methods is described below. Manual Setting via Map * Using the map in the GCS, drag the map around and zoom in to your current location. * Once you have determined your location as accurately as possible, right-click to bring up the context menu. * Select "Set the home location" from the menu. * You will be promoted to enter the altitude in metres relative to the WGS84 geoid. * The value entered into this dialog box should be the WGS84 altitude in metres, which is the sum of the altitude above Mean Sea Level (MSL) and the local geoid seperation: Altitude (WGS84) = Height (MSL) + Geoid Seperation When doing the calculation, be mindful of the fact that geoid separation can be positive or negative, so take the sign into consideration! One way to determine the height above seal level is to use the free Google Earth application. Once you have determined your position, carefully place the mouse over your location; the height above sea level will be shown in the lower right hand corner of the screen. * To determine the geoid separation, one can use an online tool to obtain the value in metres. Automatic Setting with active GPS Fix * This is the preferred method of setting the Home Location and should be performed each time you use the autonomous flight features of the Revolution such as Return To Base, and way point navigation. * A good GPS fix is required so ensure that the vehicle is powered and has a clear view of the sky. * Monitor the GPS data via the GPS Display gadget on the System Page in the GCS. Keep an eye on the P DOP and the number of satellites used. * Once a good fix has been obtained, use the UAV Object browser on the System Tab and locate the Home Location UAVObject. Change the "Set" field to "FALSE". * Click on the Red Up arrow at the top of the window to save the setting. * After a few seconds the Home Location UAVObject will be updated with data from the GPS, and the "Set" field will return to TRUE. * The Home Location has now successfully been set by the Revolution with the altitude in the correct format.